The present invention relates to apparatus for treating perforated webs of cigarette paper, imitation cork, tipping paper or like material. More particularly, the invention relates to apparatus which can be used with advantage for the treatment of webs whose perforations are formed by burning holes in the material of the web. Still more particularly, the invention relates to apparatus for treating running webs of perforated cigarette paper, tipping paper or like material subsequent to the making of perforations by resorting to heat generating means.
Many manufacturers of cigarettes and analogous smokers' products believe that the admission of cool atmospheric air into the column of hot tobacco smoke which passes through a lighted cigarette will reduce the presumably deleterious effects of smoke upon the health of the smoker. Therefore, numerous brands of cigarettes exhibit wrappers which are formed with perforations, e.g., in the region where the filter mouthpiece of a filter cigarette is connected with the tobacco-containing portion. The perforations can be made in cigarette paper, in the paper which is used to form the wrapper of a filter rod, or in the so-called tipping paper which is used to connect filter mouthpieces with cigarettes of unit length or multiple unit length, e.g., in so-called filter tipping machines. Examples of such machines are those known as MAX and MAX-S, both manufactured by the assignee of the present application. Commonly owned U.S. Pat. No. 4,277,678, granted Jul. 7, 1981 to Wahle et al., discloses a MAX-S filter tipping machine. The disclosure of this patent is incorporated herein by reference. Tipping paper is normally a web of cigarette paper, imitation cork or a like material one side of which is coated (at least in part) with a suitable adhesive before the leader of the web is subdivided into a succession of discrete uniting bands which are draped around filter mouthpieces and around the adjoining end portions of plain cigarettes to form filter cigarettes of unit length or multiple unit length.
Devices which are used to form perforations in tipping paper, cigarette paper or a like material include apparatus utilizing sets of needles or like mechanical piercing implements, apparatus which resort to one or more laser beams, and apparatus which utilize one or more pairs of electrodes whose electrodes are disposed at the opposite sides of the path for a running web and which are connected with sources of high-voltage impulses, e.g., in a manner as disclosed in commonly owned U.S. Pat. No. 4,247,754, granted Jan. 27, 1981 to Baier, whose disclosure is incorporated herein by reference. It has been found that, particularly when the perforations in a running web of tipping paper or the like are made by resort to heat, the appearance of the perforated portion of the web is often quite unsatisfactory so that the web can detract from the appearance of the ultimate product, especially since the perforated portion of the web is normally visible in the wrapper of a filter cigarette or a like smokers' product. The appearance of webs whose perforations are made by resort to pairs of heat-generating electrodes, i.e., as a result of burning or charring of the material of the web, is adversely affected for several reasons, for example, because some fragments of charred web material adhere to uncharred parts of the web, because the dimensions of the holes are not sufficiently uniform due to the presence of burned or partially combusted material in certain perforations, and/or others. On the other hand, the making of holes or perforations by resort to apparatus which combust selected portions of the running web is a very effective technique which is desirable for several reasons, e.g., because the apparatus takes up little room, because the perforations can be made at the rate at which the web must be transported in a high-speed filter tipping or like machine, because the combined cross-sectional area of perforations can be regulated with a high degree of accuracy and/or because the apparatus is not very complex and is not prone to malfunction.